A continuous casting machine, which manufactures a cast slab, includes a mold and a secondary cooling zone that is disposed on the downstream side of the mold and cools a cast slab drawn from the mold while conveying the cast slab in the drawing direction (casting direction). Rollers and a plurality of cooling nozzles are provided in the secondary cooling zone. The rollers are disposed on the surface and back of the cast slab drawn from the mold, and convey (support) the cast slab while the cast slab is interposed between the rollers in a thickness direction. The plurality of cooling nozzles are disposed between the rollers adjacent to each other in a drawing direction, and cool the cast slab that is conveyed by the rollers. There is a case where the rollers provided in the secondary cooling zone are formed by integrating a plurality of rollers with roller segments and a case where the roller segments are not be used.
In the above-mentioned secondary cooling zone, cooling is important for the progress of the solidification of a cast slab and the prevention of quality defects such as cracking of a cast slab, which are caused by supercooling, is also important. For this reason, it is important to measure the surface temperature of the cast slab.
The measurement of the temperature of the surface of the cast slab is not merely simple sporadic measurement of temperature, and the steady measurement of temperature has started to be performed as a quality control index in recent years. Further, as manufacturing quality improves, the improvement of measurement accuracy and the measurement over the entire width direction have started to be required.
When the measurement of the temperature of the surface of a cast slab is steadily performed, keeping measurement accuracy for a long time is essential in a temperature measuring device. The following invention is disclosed in order to solve the above-mentioned problem.
Patent Document 1 discloses a method that temporarily stops the spraying of secondary cooling water to a temperature measurement range of the surface of the cast slab in order to suppress the effect of steam at the time of the measurement of the surface temperature of a cast slab and measures the surface temperature of the cast slab while the generation of steam by the secondary cooling water is suppressed. Patent Document 2 discloses a method that suppresses the effect of steam and the like at the time of the measurement of the surface temperature of a cast slab by surrounding a measurement portion with a hood and purging the air in the hood.